The present disclosure relates generally to switched reluctance machine (“SRM”) controls, and in particular to systems and methods to mitigate and/or manipulate the noise and vibration produced by an operating SRM, including manipulating the noise and vibration profile of the SRM and any associated driveline components. Methods, systems, and SRM controllers implementing these methods are described.
Over the recent decades, the switched reluctance machine has gained much attention in academia, industry, and defense. SRMs have advantages over competing motive technologies, including low production costs due to simple geometry, relatively low materials cost, durability in harsh conditions, and tolerance to phase winding faults. Nevertheless, SRMs can be prone to excessive vibration and acoustic noise, generated by a variety of sources including structural deformation, magnetic torque harmonics resulting from the stator-rotor interaction, machine imbalances, and load-induced imbalances. Vibration can reduce the lifetime of drivetrain and the surrounding components. In addition, the resulting noise may be bothersome to the user and environment, and in some cases indicate the signature of the source of noise.
Known systems and methods of vibration and noise manipulation in SRMs are not entirely satisfactory for the range of applications in which they are employed. Previous research has been conducted on control methods of torque ripple mitigation (TRM) in SRMs. Prior art methods of TRM in SRMs are directed to open-loop control, in which a look-up table based on machine characterization of an ideal SRM model is created off-line and used to modify the current profile to mitigate the torque ripples. However, as open-loop control is predominantly accomplished using parameters that are predetermined prior to implementation, such control has the main drawback of being sensitive to machine parameter variations that arise after the machine characterization has been implemented. This is a critical problem for open-loop control of SRMs, as SRMs are subject to relatively large parameter deviations in implementation and use due to the use of relatively cheap materials, operation over wide range of flux densities, and the non-linear relationship between current waveform and flux density as a function of the rotor position. Therefore, open-loop control that is based on the knowledge of model SRM parameters can become much less effective in reality.
This problem can be somewhat mitigated by using parameters measured for each SRM with its specific load in place. However, such a technique would then limit controller use to the specific SRM and load combination; if any components of the driveline are changed, the parameters would need to be recomputed and the controller updated. Because of this, determining parameters for each specific SRM-load combination isn't realistic for applications requiring the mass deployment of SRMs or where interchangeability of components is desired.
In contrast to open-loop control, closed-loop control uses vibration or noise measurement feedback as a direct input into the controller, replacing the off-line calibrated look-up table. Closed-loop controllers provide benefits such as immunity to machine parameter deviation, real-time monitoring of the SRM's vibratory (or noise) profile, and the ability to implement optimization methods to enable tuning of the SRM while running. However, closed-loop controls tend to be less responsive and less robust at transients resulting from load changes, as the convergence coefficient in the optimization method requires fine tuning at different load conditions beyond the capabilities of existing closed-loop systems. Moreover, the existing current harmonic profiling techniques can only mitigate torque ripples with a harmonic order number higher than the phase number. Closed-loop controllers have no control over lower frequency torque ripples, such as 1st and 2nd order harmonics. In addition, prior art closed-loop control has been applied for TRM of permanent magnet synchronous machines (PMSMs), including brushless DC motors (BDCMs) only. The inverter topology and system matrices are fundamentally different for a PMSM/BDCM in comparison to an SRM.
Thus, there exists a need for systems and methods for vibration and noise manipulation in switched reluctance machines that improve upon and advance the design of known systems and methods of SRM control. Examples of new and useful systems and methods relevant to the needs existing in the field are discussed below.
Disclosure addressing one or more of the identified existing needs is provided in the detailed description below. Examples of references relevant to systems and methods for vibration and noise manipulation in switched reluctance machine drivetrains include U.S. Pat. Nos. 8,018,193 and 7,117,754.
The '193 patent is directed to a torque ripple mitigation controller with vibration sensor delay compensation. The '754 patent is directed to a torque ripple sensor and mitigation mechanism. Unlike the disclosed invention, both the '193 and '754 patents are directed to torque ripple mitigation in a permanent magnet synchronous machine, do not include mitigation of non-torque induced vibrations such as vibrations from SRM loads or machine imbalances, and do not disclose manipulation of drive currents to accomplish goals other than vibration reduction, such as noise shaping. The complete disclosures of the above patents and patent applications are herein incorporated by reference for all purposes.